Phenolic off-flavour problems caused by saccharomyces wild yeast.

Ryder, D.S., Murray, J.P. and Stewart, M.

Abstract
A 'phenolic' off flavour problem in lager beers has been manifest at infrequent intervals in Southern Africa during the last twenty years. The cause of this off flavour had, historically, proved particularly evasive. A recurrence of the off flavour in late 1975 prompted a concerted programme of investigation which showed that the cause was due to a process control contamination with a nonculture Saccharomyces sp. Of interest are the phenolic compounds contributing to the off flavour and the use that was made of yeast plating techniques, immunofluorescence and organoleptic procedures to detect low levels of wild yeast contamination related to the recognition, control and eradication of the problem. The investigation highlighted areas that are presently under study. These include the conditions responsible for the gain of ascendency of the 'phenolic' yeast in process fermentation and environmental and seasonal aspects with reference to this type of contamination.
Keywords: brewing contamination flavour immunology off flavour phenol wild yeast